TheVirginia opossum is the only species found in the United States and Canada. It is often simply referred to as anopossum; in North America, it is commonly referred to as apossum[3] (/ˈpɒsəm/; sometimes rendered as'possum in written form to indicate the dropped "o"). TheAustralasian arboreal marsupials of suborderPhalangeriformes are also called possums because of their resemblance to opossums, but they belong to a different order. The opossum is typically a nonaggressive animal and almost never carries the virus that causesrabies.[4]
The wordopossum is derived from thePowhatan language and was first recorded between 1607 and 1611 byJohn Smith (asopassom) andWilliam Strachey (asaposoum).[5]Possum was first recorded in 1613. Both men encountered the language at the English settlement ofJamestown, Virginia, which Smith helped to found and where Strachey later served as its first secretary.[6] Strachey's notes describe the opossum as a "beast in bigness of a pig and in taste alike," while Smith recorded it "hath an head like a swine ... tail like a rat ... of the bigness of a cat."[6] The Powhatan word ultimately derives from aProto-Algonquian word (*wa·p-aʔθemwa) meaning "white dog or dog-like beast."[6]
Following the arrival of Europeans inAustralia, the termpossum was borrowed to describe distantly relatedAustralian marsupials of the suborderPhalangeriformes,[7] which are more closely related to other Australian marsupials such as kangaroos.
Didelphimorphia comes from theAncient Greek words for "two" (di) and "wombs" (delphus).[8]
Opossums are often considered to be "living fossils",[9] and as a result they are often used to approximate the ancestraltherian condition in comparative studies.[9][10] But this is a mistake, because the oldest opossum fossils are from a more recent epoch, the earlyMiocene (roughly 20 million years ago).[11] The last common ancestor of all living opossums dates approximately to theOligocene-Miocene boundary (23 million years ago) and is at most no older than Oligocene in age.[12][13] Many extinct metatherians, such asAlphadon,Peradectes,Herpetotherium, andPucadelphys, were once considered to be early opossums, but it has since been recognized that this was solely on the basis ofplesiomorphies; they are now considered to belong to older branches ofMetatheria that are only distantly related to modern opossums.
Opossums probably originated in theAmazonia region of northern South America, where they began their initial diversification.[14] They were minor components of South American mammal faunas until the late Miocene, when they began to diversify rapidly.[12] Before that time, theecological niches presently occupied by opossums were occupied by other groups of metatherians such aspaucituberculatans[15] andsparassodonts.[13][16][17]Large opossums likeDidelphis show a pattern of gradually increasing in size over geologic time assparassodont diversity declined.[16][17] Several groups of opossums, includingThylophorops,Thylatheridium,Hyperdidelphys, and sparassocynids developed carnivorous adaptations during the late Miocene-Pliocene, before the arrival ofcarnivorans in South America. Most of these groups, with the exception ofLutreolina, are now extinct.[18] It has been suggested that the size and shape of the ancestral didelphid's jaw would most closely match that of the modernMarmosa genus.[19]
Didelphimorphs are small to medium-sized marsupials that grow to the size of a house cat. They tend to be semi-arborealomnivores, although there are many exceptions. Most members of this order have longsnouts, a narrowbraincase, and a prominentsagittal crest. Thedental formula is:5.1.3.44.1.3.4 × 2 = 50 teeth. Bymammalian standards, this is an unusually full jaw. The incisors are very small, the canines large, and the molars aretricuspid.
Although all living opossums are essentially opportunisticomnivores, different species vary in the amount of meat and vegetation they include in their diet. Members of theCaluromyinae are essentiallyfrugivorous; whereas thelutrine opossum andPatagonian opossum primarily feed on other animals.[22] Thewater opossum or yapok (Chironectes minimus) is particularly unusual, as it is the only living semi-aquatic marsupial, using its webbed hindlimbs to dive in search of freshwater mollusks and crayfish.[23] The extinctThylophorops, the largest known opossum at 4–7 kg (8.8–15.4 lb), was a macropredator.[24][25][26] Most opossums arescansorial, well-adapted to life in the trees or on the ground, but members of theCaluromyinae andGlironiinae are primarily arboreal, whereas species ofMetachirus,Monodelphis, and to a lesser degreeDidelphis show adaptations for life on the ground.[27]Metachirus nudicaudatus, found in the upperAmazon basin, consumes fruit seeds, smallvertebrate creatures like birds and reptiles andinvertebrates likecrayfish andsnails, but seems to be mainlyinsectivorous.[28]
As marsupials, female opossums have a reproductive system that includes a bifurcatedvagina and a divideduterus; many have apouch.[29] The average estrous cycle of theVirginia opossum is about 28 days.[30] Opossums do possess aplacenta,[31] but it is short-lived, simple in structure, and, unlike that of placental mammals, not fully functional.[32] The young are therefore born at a very early stage, although thegestation period is similar to that of many other small marsupials, at only 12 to 14 days.[33] They give birth to litters of up to 20 young.[34] Once born, the offspring must find their way into the marsupium, if present, to hold on to and nurse from a teat. Baby opossums, like their Australian cousins, are called joeys.[35] Female opossums often give birth to very large numbers of young, most of which fail to attach to ateat, although as many as 13 young can attach,[36] and therefore survive, depending on species. The young areweaned between 70 and 125 days, when they detach from the teat and leave the pouch. The opossum lifespan is unusually short for a mammal of its size, usually only one to two years in the wild and as long as four or more years in captivity.Senescence is rapid.[37]Opossums are moderatelysexually dimorphic with males usually being larger, heavier, and having largercanines than females.[36] The largest difference between the opossum and non-marsupial mammals is the bifurcated penis of the male and bifurcated vagina of the female (the source of the termdidelphimorph, from the Greekdidelphys, meaning "double-wombed").[38] Opossum spermatozoa exhibit sperm-pairing, forming conjugate pairs in theepididymis. This may ensure thatflagella movement can be accurately coordinated for maximalmotility. Conjugate pairs dissociate into separate spermatozoa before fertilization.[39]
Opossums are usually solitary and nomadic, staying in one area as long as food and water are easily available. Some families will group together in ready-made burrows or even under houses. Though they will temporarily occupy abandoned burrows, they do not dig or put much effort into building their own. As nocturnal animals, they favor dark, secure areas. These areas may be below ground or above.[40][41]
Juvenile Virginia opossum hissing defensively
When threatened or harmed, they will "play possum", mimicking the appearance and smell of a sick or dead animal. This physiological response is involuntary (like fainting), rather than a conscious act. In the case of baby opossums, however, the brain does not always react this way at the appropriate moment, and therefore they often fail to "play dead" when threatened. When an opossum is "playing possum", the animal's lips are drawn back, the teeth are bared, saliva foams around the mouth, the eyes close or half-close, and a foul-smelling fluid is secreted from theanal glands. The stiff, curled form can be prodded, turned over, and even carried away without reaction. The animal will typically regain consciousness after a period of a few minutes to four hours, a process that begins with a slight twitching of the ears.[42]
Some species of opossums haveprehensile tails, although dangling by the tail is more common among juveniles. An opossum may also use its tail as a brace and a fifth limb when climbing. The tail is occasionally used as a grip to carry bunches of leaves or bedding materials to the nest.[43] A mother will sometimes carry her young upon her back, where they will cling tightly even when she is climbing or running.
Threatened opossums (especially males) will growl deeply, raising their pitch as the threat becomes more urgent. Males make a clicking "smack" noise out of the side of their mouths as they wander in search of a mate, and females will sometimes repeat the sound in return. When separated or distressed, baby opossums will make a sneezing noise to signal their mother. The mother in return makes a clicking sound and waits for the baby to find her. If threatened, the baby will open its mouth and quietly hiss until the threat is gone.[44]
Opossums eat insects,rodents, birds, eggs, frogs, plants, fruits and grain. Some species may eat the skeletal remains of rodents androadkill animals to fulfill their calcium requirements.[45] In captivity, opossums will eat practically anything including dog and cat food, livestock fodder and discarded human food scraps and waste.
Many large opossums (Didelphini) are immune to the venom of rattlesnakes and pit vipers (Crotalinae) and regularly prey upon these snakes.[46] This adaptation seems to be unique to the Didelphini, as their closest relative, thebrown four-eyed opossum, is not immune to snake venom.[47] Similar adaptations are seen in other small predatory mammals such asmongooses andhedgehogs. Didelphin opossums and crotaline vipers have been suggested to be in anevolutionary arms race. Some authors have suggested that this adaptation originally arose as a defense mechanism, allowing a rare reversal of an evolutionary arms race where the former prey has become the predator,[48] whereas others have suggested it arose as a predatory adaptation given that it also occurs in other predatory mammals and does not occur in opossums that do not regularly eat other vertebrates.[15] Thefer-de-lance, one of the most venomous snakes in theNew World, may have developed its highly potent venom as a means to prey on or a defense mechanism against large opossums.[48]
D. virginiana range, including introductions in the west. These areas expanded northwards (e.g., into Wisconsin and Minnesota).[49]
Opossums are found in North, Central, andSouth America. The Virginia opossum lives in regions as far north asCanada and as far south as Central America, while other types of opossums only inhabit countries south of the United States.[50] The Virginia opossum can often be found in wooded areas, though its habitat may vary widely.[51] Opossums are generally found in areas like forests, shrubland, mangrove swamps, rainforests and eucalyptus forests.[52] Opossums have been found moving northward.[49][53]
InDominica,Grenada,Trinidad,Saint Lucia andSaint Vincent and the Grenadines, thecommon opossum ormanicou is popular and can only be hunted during certain times of the year owing to overhunting.[70] The meat is traditionally prepared by smoking, then stewing. It is light and fine-grained, but the musk glands must be removed as part of preparation. The meat can be used in place of rabbit and chicken in recipes. Historically, hunters in the Caribbean would place a barrel with fresh or rotten fruit to attract opossums that would feed on the fruit or insects.
In northern/central Mexico, opossums are known astlacuache ortlacuatzin. Their tails are eaten as afolk remedy to improve fertility.[71] In the Yucatán peninsula they are known in theYucatec Mayan language as "och"[72] and they are not considered part of the regular diet by Mayan people, but still considered edible in times of famine.
^abcSiebert, Frank T. Jr. (1975). "Resurrecting Virginia Algonquian from the Dead: The Reconstituted and Historical Phonology of Powhatan". In Crawford, James Mack (ed.).Studies in Southeastern Indian Languages. University of Georgia Press.
^"Didelphimorphia".Wordnik. Retrieved14 June 2024.
^abcdKrause, William J.; Krause, Winifred A. (2006).The Opossum: Its Amazing StoryArchived 2012-12-11 at theWayback Machine. Department of Pathology and Anatomical Sciences, School of Medicine, University of Missouri, Columbia, Missouri. p. 39
^abJansa, Sharon A.; Barker, F. Keith; Voss, Robert S. (March 2014). "The Early Diversification History of Didelphid Marsupials: A Window into South America's "splendid Isolation"".Evolution.68 (3):684–695.doi:10.1111/evo.12290.PMID24125654.S2CID10274949.
^abEngelman, Russell K.; Anaya, Federico; Croft, Darin A. (27 June 2018). "Australogale leptognathus, gen. et sp. nov., a Second Species of Small Sparassodont (Mammalia: Metatheria) from the Middle Miocene Locality of Quebrada Honda, Bolivia".Journal of Mammalian Evolution.27 (1):37–54.doi:10.1007/s10914-018-9443-z.S2CID49473591.
^Vieira, Emerson R.; De Moraes, D. Astua (2003). "Carnivory and insectivory in Neotropical marsupials".Predators with Pouches: the biology of carnivorous marsupials. Csiro Publishing. pp. 267–280.ISBN978-0-643-06634-2.
^Prevosti, Francisco J.; Forasiepi, Analía; Zimicz, Natalia (2011). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?".Journal of Mammalian Evolution.20:3–21.doi:10.1007/s10914-011-9175-9.hdl:11336/2663.S2CID15751319.
^Cenizo, Marcos; Soibelzon, Esteban; Magnussen Saffer, Mariano (2015). "Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): New ichnological and taphonomic evidence".Historical Biology.28 (8):1026–1040.doi:10.1080/08912963.2015.1089868.S2CID83862150.
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^Moore, H.D. (1996). "Gamete biology of the new world marsupial, the grey short-tailed opossum, monodelphis domestica".Reproduction, Fertility, and Development.8 (4):605–15.doi:10.1071/RD9960605.PMID8870084.
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